In such a filtration apparatus, correct flocculation increases the amount of free water in the treated mixture so that drainage through the filter element or elements is rapid, but the cost of the polymers added to the sludge or slurry to be filtered or dewatered as flocculants is a very considerable item in the running costs and can approximate to the capital cost of the machine in a single year.
The degree of flocculation increases with increasing polymer content to an optimum percentage but then falls only slowly, so that there is little penalty, other than increased cost, attached to overdosing. Moreover, the material to be treated tends to vary in quality so there is consequently a tendency to add excess polymer. Inadequate polymer dosing causes clogging of the filtration elements and spillage.
It is accordingly an object of the invention to provide a control system for a filtration apparatus whereby maximum flocculation is obtained by addition of minimum qualities of flocculant.
It is also an object of the invention to provide a control system for a filtration apparatus whereby throughput of material to be treated may be maximized.
It is also an object of the invention to provide a control system for a filtration apparatus whereby at least substantially automatic operation of the apparatus can be effected.
It is also an object of the invention to provide a method of operation of a filtration apparatus whereby consumption of flocculant can be minimized without adverse effect on efficient filtering.